Measurement of Product Pellets Flow Rate

ABSTRACT

A process is described that includes flowing a carrier fluid through a transfer line, feeding polymer pellets into the transfer line at a feed location, measuring a first pressure value of the carrier fluid at a location in the transfer line upstream of the feed location, measuring a second pressure value of the carrier fluid and polymer pellets at a downstream location in the transfer line which is downstream of the feed location, and determining a mass flow rate of the polymer pellets flowing in the transfer line based on a differential pressure between the first pressure value and the second pressure value.

This application is a divisional of and claims priority to U.S. patentapplication Ser. No. 15/137,472 filed Apr. 25, 2016, published as U.S.Patent Application Publication No. 2017/0305689 A1, and entitled“Measurement of Product Pellets Flow Rate,” which is incorporated byreference herein in its entirety.

TECHNICAL FIELD

The present disclosure relates to the flow of polymer pellets from anextruder and through a transfer line.

BACKGROUND

Polymerization processes produce polymer product, often referred to as“polymer fluff”, which in many cases can be subsequently furtherprocessed in an extruder to produce polymer pellets. Components fed tothe extruder may include the polymer fluff and optional additives whichare added to the polymer fluff to impart desired characteristics (e.g.,certain mechanical, physical, and melt properties) to the extrudedpolymer pellets. The extruder, also equivalently known as a pelletizer,can convey, heat, melt, and cut the extruder feed, and the moltenpolymer mixture can be extruded (e.g., via a twin screw extruder)through a pelletizing die under select pressure to form the polymerpellets. The extruded polymer pellets are typically cooled (e.g., in airor water) at or near the discharge region of the extruder.

The extruded polymer pellets may then be transported to a productload-out area for further processing comprising storing, blending withother pellets, and/or loading into railcars, trucks, bags, supersacks,or other containers for distribution to customers. In pellet transportsystems which utilize transfer lines to move the pellets from theextruder to the load-out area, knowing the flow rate of the polymerpellets in the transfer line is desirable. The prior art suffers fromthe limitations of incomplete or inaccurate knowledge of the rate fromthe extruder, which is used to determine the appropriate amount ofstabilizer or other additive to feed to the extruder. The inventionsdescribed in the present disclosure are an improvement over the priorart.

BRIEF SUMMARY

Disclosed herein is a process comprising flowing a carrier fluid througha transfer line, feeding polymer pellets into the transfer line at afeed location, measuring a first pressure value of the carrier fluid ata location in the transfer line upstream of the feed location, measuringa second pressure value of the carrier fluid and polymer pellets at adownstream location in the transfer line which is downstream of the feedlocation, and determining a mass flow rate of the polymer pelletsflowing in the transfer line based on a differential pressure betweenthe first pressure value and the second pressure value.

Further disclosed herein is a system comprising a transfer line, acarrier fluid source positioned at a first location of the transferline, the carrier fluid source to provide a carrier fluid in thetransfer line, a polymer pellet source, the transfer line configured toreceive polymer pellets from the polymer pellet source at a secondlocation of the transfer line, the second location being downstream ofthe first location, a first pressure sensor positioned at a thirdlocation of the transfer line, the first pressure sensor to measure afirst pressure value of the carrier fluid in the transfer line at thethird location, the third location being between the first location andthe second location, a second pressure sensor positioned at a fourthlocation of the transfer line, the second pressure sensor to measure asecond pressure value of the carrier fluid containing the polymerpellets in the transfer line at the fourth location, the fourth locationbeing downstream of the second location, and a computer system coupledto the first pressure sensor and the second pressure sensor, thecomputer system configured to determining a mass flow rate of thepolymer pellets flowing in the transfer line based on a differentialpressure between the first pressure value and the second pressure value.

Also disclosed herein is a process comprising providing a carrier fluidto a transfer line at a first location, receiving, from a polymer pelletsource, polymer pellets into the transfer line at a second location, thesecond location being downstream of the first location, measuring afirst pressure value of the carrier fluid in the transfer line at athird location, the third location being between the first location andthe second location, measuring a second pressure value of the carrierfluid and polymer pellets in the transfer line at a fourth location, thefourth location being downstream of the second location, and determininga mass flow rate of the polymer pellets flowing in the transfer linebased on a differential pressure between the first pressure value andthe second pressure value.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description, reference will now be made to theaccompanying drawings in which:

FIG. 1 is a schematic illustration of the disclosed system.

DETAILED DESCRIPTION

The FIGURES described above and the written description of specificstructures and functions below are not presented to limit the scope ofwhat Applicants have invented or the scope of the appended claims.Rather, the Figures and written description are provided to teach anyperson skilled in the art to make and use the inventions for whichpatent protection is sought. Those skilled in the art will appreciatethat not all features of a commercial embodiment of the inventions aredescribed or shown for the sake of clarity and understanding. Persons ofskill in this art will also appreciate that the development of an actualcommercial embodiment incorporating aspects of the present inventionswill require numerous implementation-specific decisions to achieve thedeveloper's ultimate goal for the commercial embodiment. Suchimplementation-specific decisions may include, and likely are notlimited to, compliance with system-related, business-related,government-related and other constraints, which may vary by specificimplementation, location and from time to time. While a developer'sefforts might be complex and time-consuming in an absolute sense, suchefforts would be, nevertheless, a routine undertaking for those of skillin this art having benefit of this disclosure. It must be understoodthat the inventions disclosed and taught herein are susceptible tonumerous and various modifications and alternative forms. Lastly, theuse of a singular term, such as, but not limited to, “a,” is notintended as limiting of the number of items. Also, the use of relationalterms, such as, but not limited to, “top,” “bottom,” “left,” “right,”“upper,” “lower,” “down,” “up,” “side,” and the like are used in thewritten description for clarity in specific reference to the Figures andare not intended to limit the scope of the invention or the appendedclaims.

Described herein are systems and processes for determining a mass flowrate, a volume flow rate, or both mass and volume flow rates of polymerpellets flowing in a transfer line based on a differential pressuremeasured between two locations in the transfer line. The two locationsare generally located in the transfer line before and after polymerpellets are picked up and transported by a carrier fluid to a conveyingvelocity. The differential pressure is used to determine the extrusionmass flow rate, which can be used to control the flow of one or moreadditives to an extruder, direct the flow of polymer pellets to or awayfrom a container, and determine the mass flow rate, volume flow rate, orboth mass and volume flow rates of polymer pellets transferred to acontainer.

Turning now to the FIGURES, FIG. 1 generally illustrates a system 100which includes a polymer pellet source 110, a carrier fluid source 120,a container 140, a transfer line 130 connecting the carrier fluid source120 and the container 140, and a computer system 150 which is connectedto a first pressure sensor 132 of the transfer line 130, to a secondpressure sensor 134 of the transfer line 130, and to an optional flowsensor 136 of the transfer line 130. The computer system 150 can also beconnected to additive equipment 118 and a load cell 142 for thecontainer 140. The transfer line 130 is also connected to the polymerpellet source 110 via extruded pellet line 116.

The polymer pellet source 110 can be any source of polymer pellets. Forexample, the polymer pellet source 110 can be any extruder whichtransforms polymer product (e.g., polymer fluff or polymer powder) intopolymer pellets. The polymer product can be received from, for example,a flash tank, a degassing vessel, or fluff storage tank of apolymerization process which produces the polymer product bypolymerizing a monomer (e.g., ethylene, propylene, styrene) according totechniques known in the art. The polymer product can feed to the polymerpellet source 110 by way of polymer product line 112. In aspects wherethe polymer pellet source 110 is an extruder (also referred to as apelletizer), additive line 114 can be optionally used for mixing one ormore additives with the polymer product fed to the polymer pellet source110. Additive(s) can feed into the extruder continuously, periodically,or both continuously and periodically via additive line 114 usingadditive equipment 118 (e.g., a control valve connected to the computersystem 150 via control line 158). The extruder can heat and melt thepolymer product and the molten polymer with the additive(s) to for amolten polymer mixture. The mixture can be extruded (e.g., via a twinscrew extruder or similar extruder) through a pelletizing die underappropriate extrusion pressure to form the extruded polymer pellets. Inthe polymer pellet source 110, the extruded polymer pellets can becooled (e.g., in air or water) before flowing from the polymer pelletsource 110 via extruded pellet line 116.

For purposes of this disclosure, the term “pellet” means any discreteunit or portion of a given material, having any shape or configuration,whether regular or irregular. Thus, the term “pellet” may encompassparticles, droplets, pieces, portions, or pastilles of a given material.By the term “polymer” is meant a compound or mixture of compoundsconsisting primarily of repeating structural units called monomers, andis meant to include a prepolymer or an oligomer, that is, a polymerhaving a low molecular weight or a polymer intended as a feedstock for ahigher molecular weight polymer. The polymer may also include additivesand other processing agents as described in further detail herein.

The polymer product can be made of any polymer including low densitypolyethylene (LDPE), linear low density polyethylene (LLDPE), mediumdensity polyethylene (MDPE), high density polyethylene (HDPE), andcopolymers thereof.

The one or more additives can be any additive for producing polymerpellets known in the art. Nonlimiting examples of additives includesurface modifiers, slip agents (such as oleamide, erucamide, stearamide,behenamide, oleyl palmitamide, stearyl erucamide, ethylene his-oleamide,N,N′-Ethylene Bis(Stearamide) (EBS), including most grades of theirrespective refinement), antiblocks/anti-block agents (also called“antitack” agents) such as diatomaceous earth, tackifiers, dispersingagents, antioxidants, nucleating agents, pigments, dyes and colorants,including TiO₂, processing aids such as elastomers, waxes, oils,fluoroelastomers, antistats/anti-static agents, scavengers, odorenhancers, degradation agents, ultraviolet stabilizers, heatstabilizers, viscosity enhancers, plasticizers, delustrants, flameretardants such as antimony oxide, fillers and extenders such asalumina, silica, clays, and calcium carbonate, surfactants, lubricantssuch as talc, glass fibers, blowing agents, and combinations thereof.Any additive can be fed to the polymer pellet source 110 (such as anextruder) at a mass flow rate such that the amount of the additive isfrom about 0.0001 wt. % to about 99 wt. % relative to a mass flow rateof polymer product fed to the polymer pellet source 110 through polymerproduct line 112.

The transfer line 130 is fluidly connected to both the polymer pelletsource 110 and the carrier fluid source 120. The transfer line 130 canbe a pipe, tube, conduit, or other structure known in the art with theaid of this disclosure for fluid-flow assisted transfer of polymerpellets (e.g., pneumatic transfer). In certain aspects of thedisclosure, an exemplary diameter of the transfer line 130 can be in therange from about 15.2 cm (6 inches) to about 40.6 cm (16 inches).Pressures in the transfer line 130 can be, for example, less than about15 psig (less than about 103.4 kPa).

FIG. 1 illustrates the carrier fluid source 120 positioned at a firstlocation 160 of the transfer line 130. In FIG. 1, the transfer line 130is connected to extruded pellet line 116 of the polymer pellet source110 at a second location 162 (e.g., a feed location 162) of the transferline 130. The first location 160 and the second location 162 are spacedapart from each other, such that first location 160 is upstream of thesecond location 162. The transfer line 130 is configured to receive thepolymer pellets from the polymer pellet source 110 at the secondlocation 162 of the transfer line 130. The second location 162 of thetransfer line 130 (e.g., where the polymer pellets are received from thepolymer pellet source 110) is downstream of the first location 160 inthe transfer line 130 (e.g., where the carrier fluid source 120 ispositioned).

The transfer line 130 can have a first pressure sensor 132 positioned ata third location 164 in the transfer line 130 and a second pressuresensor 134 positioned at a fourth location 166 in the transfer line 130.The third location 164 is a location which is upstream of the secondlocation 162 (e.g., feed location 162) of the transfer line 130. Thethird location 164 can also be characterized as being between the firstlocation 160 and the second location 162. The fourth location 166 is alocation which is downstream of the second location 162 (e.g., the feedlocation) of the transfer line 130. The fourth location 166 can also becharacterized as being downstream of each of the first location 160, thesecond location 162, and the third location 164. In accordance withaspects of the present invention, the distance between the secondlocation 162 (e.g., the feed location) and the fourth location 166(e.g., the downstream location) in the transfer line 130 can be fromabout 0.5 meter (1.6 ft) to about 15 meters (49.2 ft); alternatively,from about 0.5 meter (1.6 ft) to about 10 meters (32.8 ft);alternatively, from about 1 meter (3.28 ft) to about 15 meters (49.2ft); alternatively, from about 3 meters (9.8 ft) to about 6 meters (19.7ft); alternatively, from about 2 meters (6.6 ft) to about 5 meters (16.4ft).

The first pressure sensor 132 is configured to measure a first pressurevalue of the carrier fluid (absent polymer pellets) in the transfer line130 at the third location 164. The second pressure sensor 134 isconfigured to measure a second pressure value of the carrier fluidcontaining the polymer pellets in the transfer line 130 at the fourthlocation 166. The first pressure sensor 132, the second pressure sensor134, or both the first and second pressure sensors 132 and 134 caninclude any pressure sensor of any type (e.g., electronic, pneumatic,mechanical, or combinations thereof) which can detect and measurepressure in the transfer line 130. The first pressure sensor 132, thesecond pressure sensor 134, or both the first and second pressuresensors 132 and 134 include any instrument that measures the upstreamand downstream pressure simultaneously and transmits a signal that isproportional to the differential pressure. A nonlimiting example is theFoxboro® IDP10 Electronic Differential Pressure Transmitter (availablefrom Foxboro Eckardt GmbH, Stuttgart, Germany), which measures thedifference between two pressures applied to opposite sides of a siliconstrain gauge microsensor within the sensor assembly.

The first pressure sensor 132 can be positioned in the transfer line 130to detect the pressure at the third location 164 which is a locationbetween the carrier fluid source 120 and the second location 162, i.e.,the feed location where the transfer line 130 receives the extrudedpolymer pellets. The first pressure sensor 132 can be positioned asclose to the second location 162 as practicable. For example, the firstpressure sensor 132 is positioned equal to or less than about 6, 5, 4,3, 2, 1, or 0.5 feet upstream from the second location 162. Withoutbeing limited by theory, the portion of the transfer line 130 betweenthe carrier fluid source 120 and the second location 162 (e.g., the feedlocation where polymer pellets are received) may have a pressure dropalong the length thereof; thus, positioning the first pressure sensor132 as close to the second location 162 as practicable minimizes theincorporation of any pressure drop in the transfer line 130 which is notassociated with pickup of the polymer pellets, into the differentialpressure which is used to calculate the mass flow rate of the polymerpellets. Additionally or alternatively, the differential pressure can becorrected to account for any pressure drop not associated with pickup ofthe polymer pellets in the transfer line 130, and the third location 164where the first pressure sensor 132 is positioned in the transfer line130 may be at any point in the transfer line 130 which is between thefirst location 130 of the carrier fluid source 120 and the secondlocation 162 (e.g., the feed location). The correction of thedifferential pressure may include i) use of additional pressure sensorsto detect pressure drops not associated with the polymer pellet pickup,and ii) subtraction of any non-associated pressure drops from thedifferential pressure used to calculate/determine the mass flow rate ofthe polymer pellets.

The second pressure sensor 134 can be positioned in the transfer line130 to detect the pressure at the fourth location 166 which is alocation downstream of the second location 162 (e.g., the location wherepolymer pellets are received in the transfer line 130). The location 166of the second pressure sensor 134 is far enough from the second location162 so that the polymer pellets in the carrier fluid reach a conveyingvelocity. For example, the distance between the second location 162 andthe fourth location 166 (the location of the second pressure sensor 134)can range from about 0.5 meter (1.6 ft) to about 15 meters (49.2 ft);alternatively, from about 0.5 meter (1.6 ft) to about 10 meters (32.8ft); alternatively, from about 1 meter (3.28 ft) to about 15 meters(49.2 ft); alternatively, from about 3 meters (9.8 ft) to about 6 meters(19.7 ft); alternatively, from about 2 meters (6.6 ft) to about 5 meters(16.4 ft). Distances shorter than those disclosed herein may not allowfor appreciable acceleration of the pellets so as to cause a reliabledifferential pressure. Distances larger than those disclosed hereinintroduce frictional loss in the pressure differential signal as aresult of drag by the conveying gas and by the conveyed pellets.

The carrier fluid source 120 is configured in the system 100 to providea carrier fluid flowing in the transfer line 130. The carrier fluid canbe any fluid known in the art for transporting polymer pellets in atransfer line. Nonlimiting examples of carrier fluids include gases suchas nitrogen and a combination of oxygen and nitrogen (e.g., air);liquids such as water or a volatile organic liquid (such as an alcohol,including but not limited to ethanol, propanol, isopropanol, butanol,and mixtures thereof, and hydrocarbons having from 2 to 20 carbon atomsand/or a boiling point up to about 360° C.), and combinations thereof;and combinations of one or more gas and one or more liquid. When thecarrier fluid includes water, or an organic liquid, the carrier fluidsource 120 may be a pump, such as a variable speed displacement pump orsimilar pressure displacing device. When the carrier fluid includes agas, the carrier fluid source 120 may be a pressurized source of the gas(e.g., at a pressure higher than the pressure of the transfer line 130)or equipment known in the art which imparts movement to a gas at adesired pressure (e.g., a fan, blower, or compressor). In aspects inwhich the carrier fluid includes both gas and liquid, the carrier fluidsource 120 can be any equipment or combination of equipment known in theart which imparts movement to liquid and gas at a desired pressure inthe transfer line 130.

In accordance with aspects of the present disclosure, the carrier fluidsource 120 provides the carrier fluid (e.g., a gas such as nitrogen orair) in the transfer line 130 such that a pickup velocity of the carrierfluid at the second location 162 in the transfer line 130 is from about10 m/s (32.8 ft/s) to about 40 m/s (131.2 ft/s). The pickup velocity isthe linear velocity of the carrier fluid in the transfer line 130 justbefore contact with the polymer pellets at the second location 162 inthe transfer line 130.

Once the carrier fluid contacts (e.g., picks up) the polymer pellets atthe second location 162, the polymer pellets are accelerated to aconveying velocity. The conveying velocity is reached at a point in thetransfer line 130 between the second location 162 and the fourthlocation 166. In accordance with the present disclosure, the conveyingvelocity is from about 10 m/s (32.8 ft/s) to about 40 m/s (131.2 ft/s),and the distance between the second location 162 and the fourth location166 ranges from about 0.5 meter (1.6 ft) to about 15 meters (49.2 ft);alternatively, from about 0.5 meter (1.6 ft) to about 10 meters (32.8ft); alternatively, from about 1 meter (3.28 ft) to about 15 meters(49.2 ft); alternatively, from about 3 meters (9.8 ft) to about 6 meters(19.7 ft); alternatively, from about 2 meters (6.6 ft) to about 5 meters(16.4 ft). The conveyance of the polymer pellets by the carrier fluidcan be referred to as pneumatic conveying in a dilute phase mode, whichinvolves suspension of the polymer pellets in the carrier fluid duringtransfer through the transfer line 130. The conveying velocity of thepolymer pellets is greater than the saltation velocity (e.g., thevelocity at which the polymer pellets fall out of suspension in ahorizontal section of the transfer line 130), the choking velocity(e.g., the minimum gas velocity required to maintain the polymer pelletsin the dilute-phase mode in a vertical section of the transfer line130), or both the saltation velocity and the choking velocity.

The system 100 can optionally include a flow sensor 136. The flow sensor136, when included, is positioned in the transfer line 130 to measurethe flow rate (e.g., volumetric or mass flow rate) of the carrier fluidbefore the carrier fluid contacts the polymer pellets (before pickup).The flow sensor 136 is positioned in the transfer line 130 at a location168 which is upstream of the second location 162. Without being limitedby theory, the flow of the carrier fluid upstream of the second location162 is believed to be substantially constant; thus, the flow sensor 136can be positioned at any point of the transfer line 130 which is betweenthe first location 160 and the second location 162. In accordance withaspects of the present disclosure, the flow sensor 136 is positionedequal to or less than about 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, or 0.5 feetupstream from the second location 162. The flow sensor 136 may be of anytype known in the art (e.g., electronic, pneumatic, mechanical, orcombinations thereof) which can measure the flow of gas, liquid, or amixture of gas and liquid in the transfer line 130. The flow sensor 136includes any instrument which can detect the flow, convert the flow to asignal, and transmit the signal, e.g., to the computer system 150. Theflow rate value of the carrier fluid measured in the transfer line 130can be temperature and pressure compensated to account for differencesin temperature and pressure which depend, for example, on the time ofyear and the environmental conditions present at the time. In an aspectof the disclosure, the flow sensor 136 is used to determine the pickupvelocity of the carrier fluid in the transfer line 130.

The system 100 can also include a container 140 which receives thepolymer pellets from the transfer line 130. Nonlimiting examples whichcan embody the container include railcars, trucks, bags, supersacks,totes, or other containers which are used to distribute the polymerpellets to customers or to other equipment for further processing (e.g.,product molding such as into bottles, film, caps, buckets, toys, or carparts). The polymer pellets flow into the container 140 from thetransfer line 130, and the carrier fluid either drains from thecontainer (e.g., in aspects where the carrier fluid includes a liquid)or escapes to the atmosphere or through a flare system, or is exitedthrough a vent (e.g., in aspects where the carrier fluid includes agas).

With continued reference to the FIGURE, FIG. 1 illustrates that thesystem 100 includes a computer system 150. The computer system 150 isoperably coupled to the first pressure sensor 132 via communication line152, the second pressure sensor 134 via communication line 154, the flowsensor 136 via communication line 156, the additive equipment 118 viacommunication line 158, a load cell 142 via communication line 159, orcombinations thereof. The communication lines can include but are notlimited to equipment configured for wireless communication, cellularcommunication, Bluetooth communication, LAN communication, WANcommunication, Ethernet communication, Internet communication, wiredcommunication, pneumatic communication, or combinations thereof.

The computer system 150 can include at least one processor, at least onememory, and instructions stored on the memory which cause the computersystem 150 to perform any of the functions disclosed herein. Nonlimitingexamples of the computer system 150 include at least one desktopcomputer, at least laptop computer, at least one mobile device, at leastone controller device, at least one server, or combinations thereof.

The computer system 150 can be configured to perform one or more of thefollowing: (i) determine the mass flow rate of the polymer pelletsflowing in the transfer line 130, (ii) record the mass flow rate of thepolymer pellets which flow to the container 140 during a loading time,(iii) receive a signal regarding a mass of polymer in the container, andoptionally further process the signal (e.g., compare the signal to athreshold level to determine that the container 140 is below or at athreshold level of polymer pellets), (iv) determine a total mass ortotal volume of the polymer pellets in the container 140 based on themass flow rate of the polymer pellets recorded during the loading time,(v) divert a flow of the polymer pellets away from the container 140,(vi) determine an amount of one or more additives to feed to the polymerpellet source 110 based on the mass flow rate of the polymer pellets inthe transfer line 130, (vii) control a flow of the one or more additivesfed to the polymer pellet source 110, and/or (viii) combinationsthereof.

The mass flow rate of the polymer pellets flowing in the transfer line130 of the system 100 can be determined based on the differentialpressure between a first pressure value measured by the first pressuresensor 132 and a second pressure value measured by the second pressuresensor 134. The mass flow rate of the polymer pellets can be determinedusing Equation 1:

S=(Fg*P/(P−dP)−(Fg*(P/(P−dP)))²−(4*A ²*dP*g _(c) /d _(s))))(d_(s)/2)  (1)

where:

S is the mass flow rate of the polymer pellets in units of lb_(m)/s orkg/s,

Fg is the volumetric flow rate of the carrier fluid in units of ft³/s orm³/s,

P is the pressure value in the transfer line 130 before pickup of thepellets in units of psig or Pa (N/m²),

dP is the differential pressure in the transfer line 130 before andafter pellet pickup in units of psi or Pa (N/m²),

A is the cross sectional area of the transfer line 130 in units of ft²or m²,

g_(c) is the gravitational constant in units of lb_(m)*ft/lb_(f)/s² orN*m²/kg²,

d_(s) is the density of the polymer pellets in units of lb_(m)/ft³ orkg/m³.

The volumetric flow rate, Fg, can be measured by the flow sensor 136.The pressure value in the transfer line 130 before pellet pickup, P, canbe measured by the first pressure sensor 132. The differential pressure,dP, can be determined by measuring the pressure value in the transferline 130 after pellet pickup with the second pressure sensor 134, and bysubtracting the pressure value after pellet pickup (the second pressurevalue) from the pressure value before pellet pickup (the first pressurevalue). The cross sectional area of the transfer line 130 is calculatedbased on the known formula for area of a circle, A=π*R², where R is theradius of the transfer line 130. The gravitational constant, g_(c), is32.174 lb_(m)*ft/lb_(f)/s or 6.674×10⁻¹¹ N*m²/kg². The density of thepolymer pellets, d_(s), can be obtained from standard testingprocedures, for example, ASTM D792 or ISO 1183.

Alternatively, correlations can be developed to determine the mass flowrate of the polymer pellets in the transfer line 130. For example, themass flow rate of polymer pellets into the transfer line is measured bya pellet flow meter between the polymer pellet source 110 and thetransfer line 130 or by a polymer fluff flow meter located upstream ofthe polymer pellet source 110 (e.g., positioned in polymer product line112), and experiments can be performed to measure the differentialpressure created by various mass flow rates for a given polymer product.The collection of differential pressures can be correlated versus massflow rate of the polymer pellets, polymer fluff, or both the polymerpellets and polymer fluff, and the correlation can be used (e.g., by thecomputer system 150) to determine the mass flow rate when differentialpressure is measured. For example, the correlations can be used by thecomputer system 150 in the system 100 of FIG. 1 which has no polymerpellet flow meter or polymer fluff flow meter; alternatively, thecorrelations can be used in a pellet transfer system which has one orboth of such flow meters and uses differential pressure in the transferline to confirm the mass flow rate of polymer pellets and/or to providea mass balance versus the polymer product received by the polymer pelletsource 110.

The mass flow rate of the polymer pellets in the transfer line 130 maybe recorded by the computer system 150 in any manner known in the artfor storing information and data. For example, the computer system 150may store or record the mass flow rate data in one or more of the memoryand in a datastore operably coupled with the computer system 150 via asecure cloud storage system. The mass flow rate can be recordedcontinuously, periodically, or both continuously and periodically duringa loading time of the polymer pellets. The loading time can be aninterval of time during which the polymer pellets are transferring intothe container 140.

A signal can be received by the computer system 150 via communicationline 159. The signal can be generated by equipment such as a load cell142 which measures the total mass of the container 140 and any contentstherein. For example, the load cell 142 can measure the mass of thecontainer 140 before pellets are loaded into the container, andthereafter continuously or periodically or both periodically andcontinuously during transfer of polymer pellets into the container 140.The signal generated by the load cell 142 and received by the computersystem 150 can indicate that the container 140 is at a threshold levelof polymer pellets. The threshold level can be a mass of polymer pelletsin the container 140 which is a proper mass for the container 140 (e.g.,does not cause failure of the container 140, or is suitable for freightshipping).

The computer system 150 can determine the total mass or total volume ofthe polymer pellets in the container 140. For example, the mass orvolume of the polymer pellets can be calculated based on the mass flowrate of the polymer pellets recorded during the loading time, which asdescribed above, can be an interval of time during which the polymerpellets are transferred into the container 140. The total mass is themultiple of the mass flow rate and the interval of time. The totalvolume is the total mass times the density of the polymer pellets. Thecomputer system 150 can determine the total mass or total volume ofpolymer pellets in the container 140 in response to receiving the signalvia communication line 159. The computer can compare the calculatedvalue for mass or volume of polymer pellets to the value determinedbased upon the signal generated by the load cell 142.

The computer system 150 can cause the flow of the polymer pellets todivert away from the container 140. For example, the computer system 150can control a valve (not shown) in the transfer line 130 which redirectspolymer pellet flow through another portion of the transfer line 130such that polymer pellets flow to another container when a firstcontainer has reached a threshold level. In another example, thecomputer system 150 can cause a device to move the transfer line 130such that the outlet of the transfer line 130 is pointed to anothercontainer. In yet another example, the computer system 150 can cause thecontainer 140 to move (e.g., a conveyor line) such that anothercontainer arrives at the outlet of the transfer line 130. The computersystem 150 can divert the flow of polymer pellets in response toreceiving the signal via communication line 159 from the load cell 142.

In further aspects of the disclosure, the computer system 150 candetermine an amount of one or more additives to feed to the polymerpellet source 110. The determination can be based on the mass flow rateof the polymer pellets calculated in the transfer line 130. For example,if a particular additive is desired in an amount of 1 wt. % relative tothe mass flow rate of the polymer pellets in the transfer line 130, thenthe computer system 150 can determine a mass flow rate of 100 lb/s inthe transfer line 130 indicates the additive should be fed to thepolymer pellet source 110 at a rate of 1 lb/s (0.45 kg/s).

The computer system 150 can also control a flow of the one or moreadditives fed to the polymer pellet source 110. For example, havingcalculated the mass flow rate of polymer pellets in the transfer line130, the computer system 150 can cause the equipment 118 which feeds anyadditive to the polymer pellet source 110 to adjust or maintain the flowrate of said additive such that the amount of the additive fed to thepolymer pellet source 110 is at the determined amount. The amount ofadditive determined by the computer system 150 can be from about 1 ppmto about 99 wt. % based on the mass flow rate calculated for the polymerpellets flowing in the transfer line 130.

FIG. 1 can also be used to describe aspects of the disclosed processes.In the disclosed processes, a carrier fluid (e.g., air) can flow throughthe transfer line 130 (e.g., the carrier fluid being provided by thecarrier fluid source 120 such as an air blower at the first location 160of the transfer line 130), polymer pellets (e.g., polyethylene) can feedinto the transfer line 130 at a feed location (e.g., the second location162 described hereinabove, which is downstream of the first location160), a first pressure value can be measured for the carrier fluid at alocation 164 in the transfer line 130 (e.g., the third location 164 asdescribed herein) which is upstream of the feed location 162, a secondpressure value can be measured for the carrier fluid containing thepolymer pellets at a downstream location 166 (e.g., a fourth location166 as described herein) in the transfer line 130 which is downstream ofthe feed location (e.g., the second location 162 as described herein),and a mass flow rate of the polymer pellets flowing in the transfer line130 can be determined based on a differential pressure between the firstpressure value and the second pressure value. In additional aspects ofthe processes, the polymer pellets may flow from the transfer line 130to the container 140, and the total mass or total volume of the polymerpellets in the container can be determined based on the mass flow rateof the polymer pellets recorded during a loading time of the container140. In further aspects of the processes, a flow of the polymer pelletscan be diverted away from the container 140, where determination of thetotal mass or total volume and diversion of the polymer pellets areperformed in response to one or more of a calculated determination and asignal that the container 140 is at a threshold level of polymerpellets. In some aspects, the processes can include determining anamount of one or more additives to feed to the polymer pellet source 110(e.g., an extruder) based on the determined mass flow rate of thepolymer pellets in the transfer line 130, and adjusting or maintaining aflow of the one or more additives to the polymer pellet source 110(e.g., based on the determined amount of the one or more additives tofeed to the polymer pellet source 110). Aspects of the processes canalso include accelerating the polymer pellets to a conveying velocity(e.g., from about 10 m/s (32.8 ft/s) to about 40 m/s (131.2 ft/s))between the second location 162 (e.g., feed location) and the fourthlocation 166 (e.g., the downstream location) in the transfer line 130.Additionally, aspects of the processes described herein can also includemeasuring a flow rate of the carrier fluid at a location 168 in thetransfer line 130 which is upstream of the second location 162 (e.g.,the feed location).

The disclosed and described aspects can determine the mass flow rate ofthe polymer pellets in the transfer line 130 without need for a massflow device (e.g., a mechanical pellet flow meter) in the system 100.Mass flow devices are expensive and typically add elevation to thepellet drying system and screener of the polymer pellet source 110.Moreover, positioning a mass flow device upstream of a pellet screenercan introduce debris into the mass flow device; thus, causing damage orproblems with the operation of the mass flow device. Utilizing thedisclosed features and aspects eliminates the need for a mass flowdevice, saving on capital expenditure for purchase and repair of saiddevices. Utilizing the disclosed features also lowers the elevation ofthe pellet drying system and screener of the polymer pellet source 110(e.g., by about 15 feet elevation), which reduces head pressure requiredin the pellet water hydraulic loop (e.g., reduces needed operatingpower) and reduces capital cost, since a structure for higher elevationof the polymer pellet source 110 is not needed.

While the present disclosure has been illustrated and described in termsof particular apparatus and methods of use, it is apparent thatequivalent techniques, components and constituents may be substitutedfor those shown, and other changes can be made within the scope of thepresent disclosure as defined by the appended claims.

EXAMPLES

The subject matter having been generally described, the followingexamples are included to demonstrate the practice and advantagesthereof, as well as preferred aspects and features of the inventions. Itshould be appreciated by those of skill in the art that the techniquesdisclosed in the examples which follow represent techniques discoveredby the inventors to function well in the practice of the inventions, andthus can be considered to constitute preferred modes for its practice.However, those of skill in the art should, in light of the presentdisclosure, appreciate that many changes can be made in the specificaspects which are disclosed and still obtain a like or similar resultwithout departing from the scope of the inventions of the instantdisclosure. It is understood that the examples are given by way ofillustration and are not intended to limit the specification of theclaims to follow in any manner.

Examples 1 and 2 demonstrate the determination of a mass flow rate ofpolymer pellets based on a differential pressure based on pressuresbefore and after polymer pellet pickup in a transfer line, utilizing airas the carrier fluid in the transfer line. The mass flow rate of polymerpellets in a transfer line for each of Example 1 and Example 2 wascalculated using Equation 1 above for both English and SI units.

The values for the parameters of Equation 1 in English units are shownin Table 1 below:

TABLE 1 Example 1 Example 2 Air Volumetric Flow Rate, Fg (ft³/s) 50.621.8 Pressure Before Pellet Pickup, P (psig) 11.000 10.500 DifferentialPressure, dP (psi) 4.113 1.478 Transfer Line Cross Sectional Area, A(ft²) 0.545 0.349 Gravitational Constant, g_(c) (lb_(m)*ft/lb_(f)/s²)32.174 32.174 Pellet Density, d_(s) (lb_(m)/ft³) 59.62 59.62

The values for the parameters of Equation 1 in SI units are shown inTable 2 below:

TABLE 2 Example 1 Example 2 Air Volumetric Flow Rate, Fg (m³/s) 1.430.617 Pressure Before Pellet Pickup, P (Pa) 75,842 72,395 DifferentialPressure, dP (Pa) 28,358 10,190 Transfer Line Cross Sectional Area, A(m²) 0.0506 0.0324 Gravitational Constant, g_(c) (N*m²/kg²) 6.674 ×10⁻¹¹ 6.674 × 10⁻¹¹ Pellet Density, d_(s) (kg/m³) 955 955

Substituting the values of Table 1 into Equation 1 yields the followingvalues for mass flow rate of polymer pellets in the transfer line:

TABLE 3 Example 1 Example 2 Mass Flow Rate, S (lb/s) 33.3 11.2

Substituting the values of Table 2 into Equation 1 yields the followingvalues for mass flow rate of polymer pellets in the transfer line:

TABLE 4 Example 1 Example 2 Mass Flow Rate, S (kg/s) 15.1 5.1

Examples 1 and 2 thus demonstrate that mass flow rate of polymer pelletsin a transfer line can be calculated using a differential pressure inthe transfer line 130, where the differential pressure is the differencebetween a first pressure of the transfer line before pickup of thepolymer pellets and a second pressure of the transfer line after pickupof the polymer pellets.

The pickup velocity of the air for Example 1 was 92.8 ft/s (28.3 m/s).The pickup velocity of the air for Example 2 was 62.5 ft/s (19.1 m/s).The conveying velocity of the air and polymer pellets in the transferline for Example 1 was 98.8 ft/s (30.1 m/s). The conveying velocity ofthe air and polymer pellets in the transfer line for Example 2 was 64.9ft/s (19.8 m/s).

ADDITIONAL DISCLOSURE

Accordingly, the scope of protection is not limited by the descriptionset out above but is only limited by the claims which follow, that scopeincluding all equivalents of the subject matter of the claims. Each andevery claim is incorporated into the specification as an aspect of thepresent invention. Thus, the claims are a further description and are anaddition to the detailed description of the present invention.

Aspect 1 is a process comprising flowing a carrier fluid through atransfer line, feeding polymer pellets into the transfer line at a feedlocation, measuring a first pressure value of the carrier fluid at alocation in the transfer line upstream of the feed location, measuring asecond pressure value of the carrier fluid and polymer pellets at adownstream location in the transfer line which is downstream of the feedlocation, and determining a mass flow rate of the polymer pelletsflowing in the transfer line based on a differential pressure betweenthe first pressure value and the second pressure value.

Aspect 2 is the process of Aspect 1, further comprising flowing thepolymer pellets from the transfer line to a container, and determining atotal mass or a total volume of the polymer pellets in the containerbased on the mass flow rate of the polymer pellets recorded during aloading time of the container.

Aspect 3 is the process of any of the Aspects 1 to 2, further comprisingdiverting a flow of the polymer pellets away from the container, whereinthe step of diverting and the step of determining a total mass or atotal volume of the polymer pellets are performed in response to asignal that the container is at a threshold level of polymer pellets.

Aspect 4 is the process of any of aspects 1 to 3, further comprisingdetermining an amount of one or more additives to feed to an extruderbased on the mass flow rate of the polymer pellets in the transfer line,wherein the extruder is a source of the pellets fed to the transferline, and adjusting a flow of the one or more additives to the extruder.

Aspect 5 is the process of aspect 4, where the one or more additivescomprise surface modifiers, slip agents, antiblocks, tackifiers,dispersing agents, antioxidants, nucleating agents, pigments, dyes andcolorants, processing aids, waxes, oils, fluoroelastomers, antistats,scavengers, odor enhancers, degradation agents, ultraviolet stabilizers,heat stabilizers, viscosity enhancers, plasticizers, delustrants, flameretardants, fillers and extenders, surfactants, lubricants, glassfibers, blowing agents, or combinations thereof.

Aspect 6 is the process of any of aspects 1 to 5, wherein a pickupvelocity of the carrier fluid at the feed location is from about 10 m/sto about 40 m/s.

Aspect 7 is the process any of aspects 1 to 6, further comprisingaccelerating, between the feed location and the downstream location inthe transfer line, the polymer pellets to a conveying velocity.

Aspect 8 is the process of aspect 7, wherein the conveying velocity isfrom about 10 m/s to about 40 m/s.

Aspect 9 is the process of any of aspects 1 to 8, wherein a distancebetween the feed location and the downstream location is from about 1meter to about 15 meters.

Aspect 10 is the process of any of aspects 1 to 9, wherein the carrierfluid comprises nitrogen, a combination of oxygen and nitrogen, orwater.

Aspect 11 is the process of any of aspects 1 to 10, further comprisingmeasuring a flow rate of the carrier fluid upstream of the feed locationof the transfer line.

Aspect 12 is a system comprising a transfer line, a carrier fluid sourcepositioned at a first location of the transfer line, the carrier fluidsource to provide a carrier fluid in the transfer line, a polymer pelletsource, the transfer line configured to receive polymer pellets from thepolymer pellet source at a second location of the transfer line, thesecond location being downstream of the first location, a first pressuresensor positioned at a third location of the transfer line, the firstpressure sensor to measure a first pressure value of the carrier fluidin the transfer line at the third location, the third location beingbetween the first location and the second location, a second pressuresensor positioned at a fourth location of the transfer line, the secondpressure sensor to measure a second pressure value of the carrier fluidcontaining the polymer pellets in the transfer line at the fourthlocation, the fourth location being downstream of the second location,and a computer system coupled to the first pressure sensor and thesecond pressure sensor, the computer system configured to determining amass flow rate of the polymer pellets flowing in the transfer line basedon a differential pressure between the first pressure value and thesecond pressure value.

Aspect 13 is the system of aspect 12, wherein the computer system isfurther configured to record the mass flow rate of the polymer pelletsto a container during a loading time, receive a signal that thecontainer is at a threshold level, and determine a total mass or a totalvolume of the polymer pellets in the container based on the mass flowrate of the polymer pellets recorded during the loading time.

Aspect 14 is the system of aspect 13, wherein the computer system isfurther configured to divert a flow of the polymer pellets away from thecontainer, wherein the computer system determines a total mass or atotal volume of the polymer pellets and diverts a flow in response toreceiving the signal.

Aspect 15 is the system of any of aspects 12 to 14, wherein the polymerpellet source comprises an extruder, and wherein the computer system isfurther configured to determine an amount of one or more additives tofeed to the extruder based on the mass flow rate of the polymer pelletsin the transfer line, and control a flow of the one or more additives tothe extruder.

Aspect 16 is the system of any of aspects 12 to 15, wherein a pickupvelocity of the carrier fluid at the second location is from about 10m/s to about 40 m/s.

Aspect 17 is the system of any of aspects 12 to 16, wherein the polymerpellets are accelerated to a conveying velocity between the secondlocation and the fourth location in the transfer line.

Aspect 18 is the system of aspect 17, wherein the conveying velocity isfrom about 10 m/s to about 40 m/s.

Aspect 19 is the system of any of aspects 12 to 18, wherein a distancebetween the second location and the fourth location is from about 1meter to about 15 meters.

Aspect 20 is the system of any of aspects 12 to 19, wherein the carrierfluid comprises, nitrogen, a combination of nitrogen and oxygen, orwater.

Aspect 21 is the system of any of aspects 12 to 20, further comprising aflow sensor to measure a flow rate of the carrier fluid upstream of thesecond location of the transfer line, the flow sensor being coupled tothe computer system.

Aspect 22 is a process comprising providing a carrier fluid to atransfer line at a first location, receiving, from a polymer pelletsource, polymer pellets into the transfer line at a second location, thesecond location being downstream of the first location, measuring afirst pressure value of the carrier fluid in the transfer line at athird location, the third location being between the first location andthe second location, measuring a second pressure value of the carrierfluid and polymer pellets in the transfer line at a fourth location, thefourth location being downstream of the second location, and determininga mass flow rate of the polymer pellets flowing in the transfer linebased on a differential pressure between the first pressure value andthe second pressure value.

Aspect 23 is the process of aspect 22, further comprising flowing thepolymer pellets from the transfer line to a container, and determining atotal mass or a total volume of the polymer pellets in the containerbased on the mass flow rate of the polymer pellets recorded during aloading time of the container.

Aspect 24 is the process of aspect 23, further comprising diverting aflow of the polymer pellets away from the container, wherein the step ofdiverting and the step of determining a total mass or a total volume ofthe polymer pellets are performed in response to a signal that thecontainer is at a threshold level of polymer pellets.

Aspect 25 is the process of any of aspects 22 to 24, further comprisingdetermining an amount of one or more additives to feed to an extruderbased on the mass flow rate of the polymer pellets in the transfer line,wherein the extruder is a source of the pellets fed to the transferline, and adjusting a flow of the one or more additives to the extruder.

Aspect 26 is the process of aspect 25, where the one or more additivescomprise surface modifiers, slip agents, antiblocks, tackifiers,dispersing agents, antioxidants, nucleating agents, pigments, dyes andcolorants, processing aids, waxes, oils, fluoroelastomers, antistats,scavengers, odor enhancers, degradation agents, ultraviolet stabilizers,heat stabilizers, viscosity enhancers, plasticizers, delustrants, flameretardants, fillers and extenders, surfactants, lubricants, glassfibers, blowing agents, or combinations thereof.

Aspect 27 is the process of any of aspects 22 to 26, wherein a pickupvelocity of the carrier fluid at the second location is from about 10m/s to about 40 m/s.

Aspect 28 is the process any of aspects 22 to 27, further comprisingaccelerating, between the second location and the fourth location in thetransfer line, the polymer pellets to a conveying velocity.

Aspect 29 is the process of aspect 28, wherein the conveying velocity isfrom about 10 m/s to about 40 m/s.

Aspect 30 is the process of any of aspects 22 to 29, wherein a distancebetween the second location and the fourth location is from about 1meter to about 15 meters.

Aspect 31 is the process of any of aspects 22 to 30, wherein the carrierfluid comprises nitrogen, a combination of oxygen and nitrogen, orwater.

Aspect 32 is the process of any of aspects 22 to 31, further comprisingmeasuring a flow rate of the carrier fluid upstream of the secondlocation of the transfer line.

While the disclosure has been shown and described in various aspects,modifications thereof can be made without departing from the spirit andteachings of the invention. The aspects and examples described hereinare exemplary only, and are not intended to be limiting. Many variationsand modifications of the invention disclosed herein are possible and arewithin the scope of the invention.

Variations, combinations, or modifications of the features made by aperson having ordinary skill in the art are within the scope of thedisclosure. Alternative aspects that result from combining, integrating,or omitting features are also within the scope of the disclosure. Wherenumerical ranges or limitations are expressly stated, such expressranges or limitations should be understood to include iterative rangesor limitations of like magnitude falling within the expressly statedranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4,5, 6, . . . ; greater than 0.10 includes 0.11, 0.12, 0.13, 0.14, 0.15, .. . ). For example, whenever a numerical range with a lower limit,R_(l), and an upper limit, R_(u), is disclosed, any number fallingwithin the range is specifically disclosed. In particular, the followingnumbers within the range are specifically disclosed:R=R_(l)+k*(R_(u)—R_(l)), wherein k is a variable ranging from 1 percentto 100 percent with a 1 percent increment, i.e., k is 1 percent, 2percent, 3 percent, 4 percent, 5 percent, . . . 50 percent, 51 percent,52 percent . . . 95 percent, 96 percent, 97 percent, 98 percent, 99percent, or 100 percent. Moreover, any numerical range defined by two Rnumbers as defined in the above is also specifically disclosed. Use ofthe term “optionally” with respect to any element of a claim means thatthe element is required, or alternatively, the element is not required,both alternatives being within the scope of the claim. Use of broaderterms such as comprises, includes, and having should be understood toprovide support for narrower terms such as consisting of, consistingessentially of, and comprised substantially of.

Accordingly, the scope of protection is not limited by the descriptionset out above but is only limited by the claims which follow, that scopeincluding all equivalents of the subject matter of the claims. Each andevery claim is incorporated into the specification as an aspect of thepresent invention. Thus, the claims are a further description and are anaddition to the detailed description of the present invention.

What is claimed is:
 1. A process comprising: flowing a carrier fluidthrough a transfer line; feeding polymer pellets into the transfer lineat a feed location; measuring a first pressure value of the carrierfluid at a location in the transfer line upstream of the feed location;measuring a second pressure value of the carrier fluid and polymerpellets at a downstream location in the transfer line which isdownstream of the feed location; determining a mass flow rate of thepolymer pellets flowing in the transfer line based on a differentialpressure between the first pressure value and the second pressure value;determining an amount of one or more additives to feed to an extruderbased on the mass flow rate of the polymer pellets in the transfer line,wherein the extruder is a source of the polymer pellets fed to thetransfer line; and adjusting a flow of the one or more additives to theextruder based on the amount.
 2. The process of claim 1, where the oneor more additives comprise surface modifiers, slip agents, antiblocks,tackifiers, dispersing agents, antioxidants, nucleating agents,pigments, dyes and colorants, processing aids, waxes, oils,fluoroelastomers, antistats, scavengers, odor enhancers, degradationagents, ultraviolet stabilizers, heat stabilizers, viscosity enhancers,plasticizers, delustrants, flame retardants, fillers and extenders,surfactants, lubricants, glass fibers, blowing agents, or combinationsthereof.
 3. The process of claim 1, wherein the differential pressure iscalculated by subtracting the second pressure value from the firstpressure value.
 4. The process of claim 3, further comprising: beforedetermining the mass flow rate, correcting the differential pressure bysubtracting a pressure drop not associated with a pickup of the polymerpellets in the transfer line from the differential pressure.
 5. Theprocess of claim 1, wherein the mass flow rate is determined using theequation:S=(Fg*P/(P−dP)−(Fg*(P/(P−dP)))²−(4*A ²*dP*g _(c) /d _(s)))⁵)*(d _(s)/2)where: S is the mass flow rate in units of lb_(m)/s or kg/s, Fg is avolumetric flow rate of the carrier fluid in units of ft³/s or m³/s, Pis the first pressure value in units of psig or Pa (N/m²), dP is thedifferential pressure in units of psi or Pa (N/m²), A is a crosssectional area of the transfer line in units of ft² or m², g_(c) is agravitational constant in units of lb_(m)*ft/lb_(f)/s² or N*m²/kg², andd_(s) is a density of the polymer pellets in units of lb_(m)/ft³ orkg/m³.
 6. The process of claim 1, wherein the carrier fluid comprisesnitrogen, a combination of oxygen and nitrogen, or water.
 7. A systemcomprising: a transfer line; a carrier fluid source positioned at afirst location of the transfer line, the carrier fluid source configuredto provide a carrier fluid in the transfer line; a polymer pellet sourcecomprising an extruder, the transfer line configured to receive polymerpellets from the polymer pellet source at a second location of thetransfer line, the second location being downstream of the firstlocation; a first pressure sensor positioned at a third location of thetransfer line, the first pressure sensor configured to measure a firstpressure value of the carrier fluid in the transfer line at the thirdlocation, the third location being between the first location and thesecond location; a second pressure sensor positioned at a fourthlocation of the transfer line, the second pressure sensor configured tomeasure a second pressure value of the carrier fluid containing thepolymer pellets in the transfer line at the fourth location, the fourthlocation being downstream of the second location; and a computer systemcoupled to the first pressure sensor and the second pressure sensor, thecomputer system configured to i) determine a mass flow rate of thepolymer pellets flowing in the transfer line based on a differentialpressure between the first pressure value and the second pressure value,ii) determine an amount of one or more additives to feed to the extruderbased on the mass flow rate of the polymer pellets in the transfer line,and iii) control a flow of the one or more additives to the extruderbased on the amount.
 8. The system of claim 7, where the one or moreadditives comprise surface modifiers, slip agents, antiblocks,tackifiers, dispersing agents, antioxidants, nucleating agents,pigments, dyes and colorants, processing aids, waxes, oils,fluoroelastomers, antistats, scavengers, odor enhancers, degradationagents, ultraviolet stabilizers, heat stabilizers, viscosity enhancers,plasticizers, delustrants, flame retardants, fillers and extenders,surfactants, lubricants, glass fibers, blowing agents, or combinationsthereof.
 9. The system of claim 7, further comprising: additiveequipment connected to the computer system via a communication line andconnected to the extruder via an additive line.
 10. The system of claim9, wherein the computer system is configured to cause the additiveequipment to feed the one or more additives to the extruder in theamount that is determined by the computer system.
 11. The system ofclaim 9, wherein the additive equipment comprises a control valveconnected to the computer system.
 12. The system of claim 7, wherein thedifferential pressure is calculated by subtracting the second pressurevalue from the first pressure value.
 13. The system of claim 12, whereinthe computer system is further configured to correct the differentialpressure used to determine the mass flow rate, before determining themass flow rate, by subtracting a pressure drop not associated with apickup of the polymer pellets from the differential pressure.
 14. Thesystem of claim 7, wherein a distance between the second location andthe fourth location is from about 1 meter to about 15 meters.
 15. Thesystem of claim 7, wherein the carrier fluid comprises, nitrogen, acombination of nitrogen and oxygen, or water.
 16. A process comprising:providing a carrier fluid to a transfer line at a first location;receiving, from a polymer pellet source comprising an extruder, polymerpellets into the transfer line at a second location, the second locationbeing downstream of the first location; measuring a first pressure valueof the carrier fluid in the transfer line at a third location, the thirdlocation being between the first location and the second location;measuring a second pressure value of the carrier fluid and polymerpellets in the transfer line at a fourth location, the fourth locationbeing downstream of the second location; determining a mass flow rate ofthe polymer pellets flowing in the transfer line based on a differentialpressure between the first pressure value and the second pressure value;determining an amount of one or more additives to feed to the extruderbased on the mass flow rate of the polymer pellets in the transfer line;and adjusting a flow of the one or more additives to the extruder basedon the amount.
 17. The process of claim 16, where the one or moreadditives comprise surface modifiers, slip agents, antiblocks,tackifiers, dispersing agents, antioxidants, nucleating agents,pigments, dyes and colorants, processing aids, waxes, oils,fluoroelastomers, antistats, scavengers, odor enhancers, degradationagents, ultraviolet stabilizers, heat stabilizers, viscosity enhancers,plasticizers, delustrants, flame retardants, fillers and extenders,surfactants, lubricants, glass fibers, blowing agents, or combinationsthereof.
 18. The process of claim 16, wherein the differential pressureis calculated by subtracting the second pressure value from the firstpressure value.
 19. The process of claim 16, wherein the mass flow rateis determined using the equation:S=(Fg*P/(P−dP)−(Fg*(P/(P−dP)))²−(4*A ²*dP*g _(c) /d _(s)))⁵)*(d _(s)/2)where: S is the mass flow rate in units of lb_(m)/s or kg/s, Fg is avolumetric flow rate of the carrier fluid in units of ft³/s or m³/s, Pis the first pressure value in units of psig or Pa (N/m²), dP is thedifferential pressure in units of psi or Pa (N/m²), A is a crosssectional area of the transfer line in units of ft² or m², g_(c) is agravitational constant in units of lb_(m)*ft/lb_(f)/s² or N*m²/kg², andd_(s) is a density of the polymer pellets in units of lb_(m)/ft³ orkg/m³.
 20. The process of claim 16, further comprising: beforedetermining the mass flow rate, correcting the differential pressure toaccount for a pressure drop not associated with a pickup of the polymerpellets in the transfer line by subtracting the pressure drop from thedifferential pressure.